Placing the laws into effect “would be a violation of international law, namely the United Nations Single Convention on Narcotic Drugs of 1961, to which the United States is party,” said Raymond Yans, president of the International Narcotics Control Board.
The treaty, which can be read online, was signed with the conviction that "the measures taken against drug abuse must be coordinated and universal."
Cannabis is among the substances specifically named in the treaty.
"A Party shall, if in its opinion the prevailing conditions in its country render it the most appropriate means of protecting the public health and welfare, prohibit the production, manufacture, export and import of, trade in, possession or use of any such drug except for amounts which may be necessary for medical and scientific research only, including clinical trials therewith to be conducted under or subject to the direct supervision and control of the Party."
A statement by U.S. Attorney General Eric Holder that marijuana cultivation remains illegal under federal law was dismissed by the U.N. official as “good but insufficient.”